1. Field of the Invention
The present invention relates to a process for preparing narrow range alkoxylated isethionates. The narrow range alkoxylated isethionates are desirable in that they may be further processed to produce fatty acid esters of alkoxylated isethionates such as are disclosed in applicants' copending application, U.S. Ser. No. 08/045,951, filed Apr. 12, 1993. The invention relates to alkoxylated isethionate (or non-alkoxylated isethionates) prepared by said process.
2. Background of the Invention
The production of fatty acid esters of alkoxylated isethionates is disclosed in U.S. Ser. No. 08/045,951 filed Apr. 12, 1993, now allowed, and hereby incorporated by reference into the subject application.
In U.S. Ser. No. 08/045,951, alkoxylated isethionate are made either (1) by the sulfonation of corresponding chloroalkoxy alcohol or (2) by reaction of alkylene oxide and sodium isethionate or bisulfite. With regard to the second method, there is no teaching of a specific method of making a narrow range alkoxylated isethionate, let alone of a method of making it in a simple batch process. With regard to the first method, the method of the present invention is advantageous in that (1) it is cheaper (e.g., no need to buy chloroethoxy ethanol as starting reagent); (2) it is easier to process; and (3) there is some monomer distribution, which may be more desirable than having no distribution at all.
U.S. Pat. No. 2,810,747 to Sexton et al. teaches a method of producing a sodium isethionate substantially free of sodium sulfate, sodium sulfite, and other impurities. The patent is further concerned with minimizing formation of glycol and glycol ether (including glycol ether of isethionate, i.e., alkoxylated isethionates). Thus, not only does the references discourage formation of alkoxylated isethionate, but further there is clearly no teaching or suggestion of a method of producing and optimizing the formulation of alkoxylated isethionates within a narrowed alkylene oxide range.
U.S. Pat. No. 3,823,185 to Schlossman does teach a process for preparation of alkoxylated isethionates. However, this reaction involves a distilling step in which all or part of the water present in the reaction mixture is removed after a small amount of ethylene oxide has been reacted. In the only example shown, 98.7% water is removed. The reference clearly suggests that water increases polyether by-products and that use of large amounts of water should be avoided. Further, the reference neither teaches nor suggests a method of preparing an alkoxylated isethionate having not only a narrow distribution of alkylene oxide units, but also a narrow distribution having a low alkylene oxide content. Finally, there is no recognition that both temperature and stir rate must be kept below certain critical levels in order to achieve decreased levels of undesirable by-product. All of this in direct contrast to the process of the present invention where increased amounts of water (i.e., at least 10% water should be used according to the present invention) have been found to (1) increase reaction rate (2) increase narrow range alkylene oxide distribution and (3) not simultaneously increase undesirable by-product.
Further, as noted above, Schlossman does not teach or suggest the criticality of both low temperature (i.e., below about 95.degree. C.) and low stirring (i.e., below about 100 rpm, preferably about 50 rpm) to ensure that a narrow distribution of low alkylene oxide product is formed while minimizing undesirable by-products (e.g., glycols).
U.S. Pat. No. 3,029,264 to Alphen et al. teaches a process for the preparation of fatty acyl oxyalkylene sulphonates in which HOR'SO.sub.3 M is used as a starting reactant. There is no teaching at all, however, of how this starting reactant is made.
An object of this invention is to find a process for production of alkoxylated isethionate and narrow range distribution of alkylene oxide units.
A further object of the invention is to find a process for doing so while minimizing formation of undesirable by-products, e.g., glycols.
A further object of the invention is to provide a process which accomplishes the aforementioned goals without use of a catalyst and which can be accomplished in a simple, batch-like process in optimal reaction times.